924Board.org

[Silverarrow]

Guys! I got this 1980 931 from a Guy you all know as Zuffin. It came to me with a failed fuel pump(s) and some general electrical problems due to sitting unattended for years. Just so you know, you can run a 931 with just the in-line fuel pump and save yourself another $100. More to come with pics.

[John Brown]

Yes. You can. So long as the tank is not allowed to get too empty and/or you don't corner too fast. The life of the external pump will be somewhat reduced - perhaps not so much as to notice for some time.

[larso]

John, have you had an internal pump fail and notice that when you corner fast the engine stalls? Or is it your hypothesis? Just wondering because I am having this problem and debating whether to replace the internal pump. I am wondering if the external pump is sufficent enough to supply fuel when going around corners, or wether a shot internal pump will in fact definitly stop fuel flow around corners. If you've had expereince with this let me know, or is it just your hypothesis that if the internal pump fails, the gas might not flow enough when going around corners? Hopefully you've had experience so I can debate buying a new internal pump, buying just a new external pump, or buying both pumps!

I'll probably replace both pumps, but I would like to know if the internal pump is the BIG factor in the cornering and stalling fuel problem.

[John Brown]

Yes. I have experienced fuel starvation cornering due to the intank boost pump system being bad.

In my particular case it was the rubber connection between the pump and the screw-in fitting which allowed fuel to simply escape back into the tank. So only gravity head pressure was supplied to the external pump.

A full tank, lots of gravity if you will, and the car ran OK. As the tank emptied the motor would lose fuel pressure when cornering hard with about 2/3 tank or less. In normal street driving at 1/4 tank or less there was a noticable tendency to lose fuel pressure.

A failed in-tank pump will be worse because the external pump will have to suck fuel throught the failed pump.

God, Ferry Porsche, and Robert Bosch, all wanted the 924 to have 2 fuel pumps. Maybe we should pay attention!

[larso]

Even when I'm going around at about 10MPH-if I take a nice sharp turn, with the car in neutral, revving it at about 1200-1500, the car will die...or nearly stall, and then as soon as I straighten out the car, it kicks in slowly as the fuel makes its way back. I took out the internal pump yesterday and see the significance of it being in there for dirt reasons! Although I don't know why there are two fuel breather/intake holes that ARE big enough to let small dirt and metal fibers in ...I guess I'll have to replace the thing since the filter can't be changed! Maybe my dirty filter was causing the car to be really sensative, even at speeds as low as 10-20MPH. I just didn't expect the car to DIE when going around a sharp corner in an alley at slow speed, or taking a turn into my driveway, at slow speed (I'm not that much of a maniac driver!).

I've heard people say that clogged filters make the stalling symptom worse, and the filter was pretty full of filings..so I'll replace the pump.

I only wish that the filter was replaceable ON the pump, because my pump seems to spin freely when I stick a pin in there and turn the gear...it's not jammed, and I'm not sure if it's electrically ok..but it spins freely. I haven't hooked it up to power though, since it's still smelling like fuel and I don't want to blow it, or my hand up.

I ripped off the filter, and it looks like it's welded on, but has a purlator number on it. Darn. Wish it was threaded on so I coudl just test my pump, and replace the CEHAP filter if the pump was ok.

[Silverarrow]

Guys If you want to you can add a feeder pump externally. They're cheap($39) at any parts store and should wire up to the internal pump wiring. Get one that gives 25 to 35 gph. Just put it inline before the main pump. That should take the pressure off the main and make it last longer. I added a filter in the line before the main too. It caught a lot of crud. I haven't experienced any stalling on cornering since the mod. I wonder what is going on with your cars?

[Zuffen]

hey when you going to post a story about this car?

_________________
Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

[larso]

Hey good idea on the feed pump. Where did you get yours? I've installed a home made filter now, but not wanting to fork out money for an internal pump that doesn't filter properly. Do they sell these feed pumps in different sizes, or did the one you got match up to the hose size on the 931 pump anyway? I'd like to get one that has a similar nipple, so that the hose can be directly going from my filer, to the feed pump, to the external pump. Did you use any fittings or did the hose match right up?

[924martinirossi]

I run no internal pump in the 80 931 and have no problems. The intank pump sits in a well under the main tank and there is a baffel plate above it. So as long as you don't tip over the car and have gas in the tank I can't even see how the external tank would starve from fuel.

Michael

[dpw928]

The intank pumps can be replaced with a strainer, part # 928 201 081 04, like those used on the 928's that were NOT destined for hot climates. The screw in fitting and outlet tube is identical to the 931 in tank pump fittings. They cost about $28.00 from non dealer sources. The reason for two pumps was to fix a vapor locking problem when driven in stop and go traffic in hot climates.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[simsport]

You really cant tell much by just looking at the pump as it may be failing under load which is a common fault in any elec motor.

I would test its flow rate and ability to generate a pressure. Also check out the wires. It could be as simple as a loose connection. My relay failed and I remeber it was a little intermittent at first.

Cheers
Simon
PS A tuning mod for japanese turbo cars is to run a larger section set of wires to the pump. This reduces resistance, which increases volts to the pump which makes it pump more...easy!
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Blown is always best!

[Silverarrow]

The feeder Pump question you all have been asking is simple. I bought a 35 gph inline pump and installed a fram inline filter before the pump. The pump is $30 at any Jockos or NAPA and the fliter is $3 for the clear shell filter in the 3/8" size. If you all could find a 50gph pump it would be better. Maybe it will cost more but the in tank pump is $150 so anything cheaper is still a good deal. I attached the pump to the tubular mount behind the tranny and routes 3/8" fuel line up to the high pressure pump. If you look at the setup you have you can deal with the lines as you see fit. Power wires from the in-tank pump can be used to power the feeder pump. i just spliced extra wire in as needed. I strapped the feeder pump to the tube using heavy duty zip ties. They have held up for many months. The whole thing works good.
Bobby, I'll get the story posted in the next two weeks and you can see for yourself how it's been for me. I drive this car everywhere and it's not given me any REAL trouble. I love it!
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1977 924 NA no sunroof
1980 931 With a sunroof
I could be crazy, Oh yes I could!